A geochemical study was carried out on gas, water and mud samples from four mud volcanoes in Gorgan Plain, SE Caspian Sea (Iran) in order to investigate fluid primary sources and secondary processes controlling fluid chemistry. The chemical composition of light alkanes and the isotopic feature of methane indicated an origin related to a thermogenic source. Gases discharged from Neftlijeh evidenced anaerobic biodegradation processes with addition of secondary microbial methane. Chemical composition of discharged waters revealed two main groups i) brine-type Na⁺–Cl⁻ waters from Gharenyaregh and Neftlijeh mud volcanoes, which were marked by relatively high Na⁺/Cl⁻, B/Cl⁻ and Li/Cl⁻ ratios and low Ca²⁺/Cl⁻, Mg²⁺/Cl⁻ and K⁺/Cl⁻ ratios, ii) waters from Sofikam and Inche, characterized by relatively low Na⁺/Cl⁻, B/Cl⁻ and Li/Cl⁻ ratios and relatively high Ca²⁺/Cl⁻, Mg²⁺/Cl⁻ and K⁺/Cl⁻ ratios. The chemical and isotopic characteristics of the discharged waters suggest that evaporated Caspian seawater trapped in sediments is likely representing a reliable water source. The maximum formation depth at Gharenyaregh and Neftlijeh mud volcanoes were estimated at about 6 km depth whereas the generation depth of the rest was significantly shallower. Thus, the observed compositional differences can be related to the different depths of the fluid source feeding them.

The purpose of this study was to determine the contamination level, distribution, health risk and potential sources of Cr, Cd, Pb, Zn, Cu, Ni and As in 66 topsoil samples from industrial areas in Bandar Abbas County. The geoaccumulation index, pollution index and pollution load index were calculated to assess the pollution level in the industrial soils. The hazard index and carcinogenic risk were used to assess human health risk of heavy metals. Results showed that the contamination levels of heavy metals were in the descending order of Cu> Cd> Pb> Zn> As> Ni> Cr. Moreover, based on principal component analysis, Cd, Zn, Cu, and Pb originated mainly from anthropogenic sources, including power plants, oil and gas refinery, steel and zinc production factories and municipal waste landfills. For non-carcinogenic effects, hazard index of studied metals decreased in the order of Cr> As> Cd> Pb> Ni > Cu> Zn. Arsenic, chromium and cadmium were regarded as the priority pollutants. Carcinogenic risks due to Cd and As in suburban soils were within tolerable risk to human health; however, children faced more health risk in their daily life than adults via their unconscious ingestion and dermal contact pathway.

Potentially toxic elements (PTE) are considered to be dangerous threats, both for human health and the environment. Here, the contamination level, sources, and ecological risks posed by PTE were investigated in 19 topsoils from agricultural lands in the Bandar Abbas County on the southern coast of Iran. The soil fraction <63 μm was used for the analysis of the pseudototal contents of PTE (arsenic, cadmium, cobalt, chromium, copper, lead, manganese, molybdenum, nickel, vanadium, and zinc). The results were analyzed using principal component analysis (PCA) and Pearson’s correlations, different pollution indices [enrichment factor (EF), contamination factor (Cf), and modified degree of contamination (mCd), and the potential ecological risk index (PERI). The results of the pollution indices showed that the contamination levels of the studied agricultural soils are low to moderate, while the average PERI values indicate that the ecological risks of PTE range from low to high in the soils of the studied area. Correlations and PCA analyses suggest that studied elements have three possible origins: geogenic (chromium, cobalt, copper, manganese, vanadium, and zinc), anthropogenic (cadmium, nickel, phosphorus and lead) and atmospheric (arsenic) sources. These findings are helpful for the long-term assessment of PTE in the Bandar Abbas County.

Numerous political and economic crises, and successive wars in Afghanistan have put safe water resources at risk due to mismanagement in the country. In this study, groundwater quality in the Herat aquifer, western Afghanistan is evaluated by geochemical methods and quality indices. Total of 27 samples were collected and analyzed for nitrate, fluoride and trace elements. Sodium and bicarbonate are the main cation and anion, respectively. Various diagrams revealed that rock weathering and normal ion exchange may controls the major ion chemistry. Granitic or biotite gneiss rocks and leachate from the Herat urban sewage are the main sources of fluoride and nitrate, respectively. Geogenic source of the studied parameters was verified by principal component analysis (PCA). Groundwater is contaminated by F, As and U in the Northwest of the region, and by nitrate almost in the majority of samples, especially in urban areas. Water quality index (WQI) showed poor quality for 29.6% of the samples, and the best quality was observed in Southwest of the area. Also, based on heavy metal evaluation index (HEI), the highest pollution was observed in Northwestern region. Nitrate poses a serious health risk to consumers (particularly in central parts), so that non-carcinogenic risk (HQ) values ranged from 1.1 to 3 in most of the samples, and very high (> 3) non-carcinogenic risk values were observed in 4 sampling sites.